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Green walls can improve indoor air-quality by reducing concentrations of carbon dioxide (CO2) and other air pollutants. Our study focused on the spider plant, Chlorophytum comosum, and devil’s ivy, Epipremnum aureum, both common green-wall plants that have been found to be efficient CO2 absorbers. Both species have multiple variants with varying degrees of leaf green-white segmentation. Since photosynthesis depends on the concentration of leaf chlorophylls, we hypothesized that green variants are more efficient carbon absorbers than green-white variants. In addition, we tested the hypothesis that the photosynthetic rate of plants is affected by pot volume, as suggested by previous studies. We used a portable gas exchange system to determine the rate of photosynthesis of the study plants. No evidence was found for better photosynthetic performance in the green vs. green-white variants of each species. In fact, our results suggest the opposite. It was observed that a spider plants assimilated carbon more efficiently when grown in a larger pot volume. In conclusion, our study shows that in terms of carbon assimilation, green-white variants of spider plants are the better choice for indoor green walls. Their efficiency can be improved dramatically by increasing pot volume.

Green walls are becoming increasingly popular as pleasing architectural installations and functional systems in sustainable urban building designs. However, utilization of green walls as an aqueous treatment option has been primarily limited to grey water. This study evaluates select media as appropriate support for plants and microorganisms in a novel green wall system used to treat wastewater from craft and micro-breweries. The media must have hydraulic capacity to treat large volumes of brewery wastewater, be lightweight and commercially available, and provide structure for plant roots and biofilm development. Two expanded recycled glass aggregates (Growstone

La generación de residuos domiciliarios ha ido creciendo exponencialmente en las últimas décadas, para satisfacer las necesidades humanas mediante los servicios básicos como el agua potable, esta ha originado aguas grises y aguas negras, los derivados de aquello han incrementado problemas a la salud de la población, fuertes impactos ambientales a las aguas, a la atmósfera, al suelo e impactos económicos negativos en términos de devaluación de suelos. Al respecto el presente estudio realiza una investigación sobre un sistema automatizado para el tratamiento de aguas residuales domiciliarias, que pueda adaptarse a las necesidades de un hogar, presentando así un biodigestor anaerobio, que se caracteriza por ser de flujo continuo, baja carga orgánica y tener cuatro etapas de proceso, con el fin de reducir gastos, facilitar su implementación y cumplir con los requerimientos hídricos de una pared verde con medidas estándar. Se basó en el método analítico y el método hipotético deductivo, los resultados obtenidos, fueron de la pared verde, con un requerimiento hídrico de 105 litros por día, el biodigestor se adaptó para dicho requerimiento, en un contenedor plástico de 220 L de capacidad, donde se lleva a cabo un proceso automatizado que mejorará la calidad del agua, con la finalidad de usarla para el riego de una pared verde, integrando de esta forma los Objetivos de Desarrollo Sostenible proponiendo una solución que contribuya al desarrollo social y ambiental del mundo.

Exposure to indoor air pollution can have significant impact on human health and quality of life. Active living wall (ALW) is an advanced technique of the green wall concept, contributing to improve the indoor air quality (IAQ). Compared to the standard in-house mechanical systems for IAQ control, the use of this botanical biofilter (especially the ALW) has the potential to reduce the overall indoor air pollution as well as the carbon footprint of built environment. While ALW acts as a promising solution to improve the IAQ, this study aims to perform the environmental assessment of ALW system based on embodied energy (EE) theory. Although, ALW is beneficial for environment and society, however the sustainability of ALW system has been rarely analysed. In this study, the design and construction of ALW system has been assessed and key materials with high EE have been identified. Finally, recommendations have been made to enhance the design strategy that will help to reduce EE of ALW system for future sustainable built environment.

The main goal of this study is to assess the potential of green roofs and walls as a mitigation measure for the climate-change-driven growth of building energy consumption in extremely hot climates. A comprehensive, interdisciplinary methodology was developed that bridged climate change and building modeling. The residential building stock of Qatar was considered, with a two-story residential villa selected as a representative of the stock and consequently a case study. Weather scenarios were created for the years 2020, 2050, and 2080, and four building renovation scenarios were developed. The findings suggested that without any mitigation measures, residential building energy consumption in Qatar could increase by up to 9%, 17%, and 30% in 2020, 2050, and 2080, respectively. The addition of 5-cm expanded polystyrene and the installation of energy-efficient windows proved to be far more efficient than the addition of green walls and roofs under the climate conditions (30% reduction in energy consumption vs. 3%). Additionally, the environmental impact of green wall and roof maintenance, specific to Qatar, should be considered. However, in the final judgment, other positive effects of a green infrastructure (such as the effect on air quality, heat island effect, and health of the inhabitants) should be considered.

The use of wastewater (urine) as a fertilizer was shown to potentially reduce the campus wastewater load and contribute to saving in expensive wastewater treatment, while dealing with it as valuable resource. If one assumed that this wastewater fertilizer (arguably, one of the best agriculturally acknowledged fertilizers), was applied at odor appropriate and physiologically sustainable rates (Nitrogen Loading Rate (NLR) of up to 0.73 g N m-2 week-1 equivalent to 104.28 mL urine m-2 week-1 applied for 16 weeks) and considered total available area for potential green walls, it could be stated that the entire urine stream generated daily on campus (varying from 2.2 to 4.5 m3) could be accommodated on campus green walls as a valuable resource with significant benefits. In the studies on monitored plant physiological parameters under various conditions, it was observed that urine fertilizer positively affected to the food production, inflorescences and health of butterfly pea (Clitoria ternatea) plant as well as could say that it was the most suitable plant for green wall. Further integration of urban wastewater management and agriculture (urban food production) into this scenario can make it even more attractive and economically sustainable.

This research is a preliminary study of planting ornamental plants with a green wall system. This study aims to provide an overview and information about the selection of types of plants that are suitable and commonly used in making green walls and arranging selected plants in green walls system. Green wall system which is often called vertical garden is a technique to plant ornamental plants, vegetables or other types of plants with a free design that considers various resources that allow plants to grow vertically. The advantages of green walls are efficient use of soil, beautifying the environment, adding location value, cleaning the air, lowering temperature, producing oxygen and providing fresh food that is close to the surrounding environment at home. Not all types of plants can be planted vertically. Easy-to-grow plants, short appearance and slow growth are common characteristics used for green walls. The special characters of the selected plants are determined based on the group of indoor or outdoor plants. Consideration of nutritional, light, water and plant requirements will determine the success of planting and the sustainability of vertical planting.

Urban H eat I sland (UHI) mitigation research has been carried out for a long time but it requires to be sharpened to enrich mitigation strategies . In Bandung, maximum temperature has been increasing from 33 0 C to 35 0 C in 30 years. Bandung is getting hotter which can exaggerate the negative impact of UHI mainly in the downtown area. Suitable UHI mitigation strategies are needed to lower urban temperature. UHI mitigation has involved the use of heat-absorbing and covering man-made materials with vegetation such as green wall and roof system. Content analysis of UHI precedents and some preliminary studies are applied to assess prerequisites of UHI mitigation. The analysis showed adaptation opportunities of UHI mitigation strategy on buildings and environmental physical components. The mitigation strategies may vary depending on the typology of buildings (roof and wall) by using reflective materials, while outside the building by increasing vegetation to maximize evaporation to lower the temperature.

The environmental sustainability of the microalgae Nannochloropsis oceanica cultivation for total fatty acid (TFA) production was analyzed using life cycle assessment (LCA). Pilot data provided by the plant operator from cultivation in Italy using Green Wall Panel (GWP®) photobioreactors were upscaled to a 20-ha production process, and an LCA was conducted and assessed for the Italian regions of Tuscany and Sicily. Two additional scenarios were modelled to analyze the influence of more sustainable framework conditions, respectively nutrient recycling and renewable energy supply. The results show that environmental impacts per functional unit are around 15% less at the site with optimal growth conditions. Between 60 and 80% of the impacts are due to the energy demand during plant operation, infrastructure, and nutrient demand. Nutrient recycling and the gain of an energy credit from the separated biocrude with the hydrothermal liquefaction (HTL) process reduce the environmental impacts in all six International Reference Life Cycle Data System (ILCD) impact categories by an average of 11% compared to a scenario without nutrient recycling. The additional consideration of a renewable energy supply allows for an average reduction of 36% and together with the nutrient recycling of an average of 45% for the global warming potential (GWP) and most of the other impact categories.

The thermal benefits of Vertical Greenery System (VGS) in providing thermal comfort, reducing internal building temperature, and lowering operational energy consumption are not widely known. There is a lack of research and technical knowledge on the effects of vertical greenery systems related to thermal performance, especially in tropical climates, such as that of Malaysia. Therefore, this paper addresses this gap by investigating the effect of VGS on heat transfer and the thermal performance of hypothetical buildings. In this paper, a data prediction method is used to identify the overall thermal transfer value (OTTV) from several hypothetical case studies. A variety of combinations of variables have been used to identify the best design with the lowest OTTV reduction through VGS. From the calculation, Linear Greenery System achieved the highest OTTV reduction with an average of 6.87%, followed by Modular Green Wall (6.82%), Double-skin Green Facades (2.97%), and Direct Green Facades (1.32%). Therefore, this paper can conclude that Linear Green Wall is the best greenery system for reducing heat transfer for the tropical climate of Malaysia.

Vertical greening systems can help mitigate the urban heat islands, increase the thermal efficiency of the buildings, save cooling energy and enhance air quality by using the vegetation's natural processes. However, since vertical greening schemes need materials and energy to be built, there are questions about whether they actually deserve to be adopted and how their environmental efficiency can be improved. The study aims to evaluate verticalgreening systems' environmental efficiency and to study essential factors for efficient and sustainable building construction.

Underground green corridors are getting popular worldwide intending to integrate greenery into built environments. Green corridors provide greenery benefits and aesthetic pleasing view. Proper irrigation is necessary to maintain live plants in green walls. Automated irrigation with adequate amounts and proper drainage is vital to avoid overflows and drowning of plants. Due to improper irrigation plants in green walls can die quickly, creating a potential fire risk in underground green corridors. This paper aims at investigating the ignition, fire propagation and smoke propagation in underground green corridors. Numerical simulations with computational fluid dynamics (CFD) and physical scale modeling experiments were performed. The simulation has been completed based on heat release rate (HRR, kW/m2) data obtained from the cone calorimeter experiments for three plant species, namely; Hedera helix, Peperomia obtusifolia and Aglaonema commutatum. CFD simulations were conducted for an underground passage with a green wall. Results showed that a fire does not occur in underground corridors with fresh and live plants. However, fire risk increases gradually with drying out of plants. For dry plants, the surface temperature may reach above 850 °C. The fire spreads rapidly in about 20 s. An experimental study was carried out on a reduced-scale underground green corridor to investigate the fire and smoke propagation. It is observed that in the vertical direction fire spreads up to the ceiling rapidly. However, fire spreads slowly in the horizontal direction along the green wall. The experiments show that when the green wall is ignited, it may tremendously affect the evacuation due to smoke spread along the corridor and fire propagation in the vertical direction. It is recommended to decrease the fire risk in underground corridors with properly maintained green walls, especially in evacuation paths. This work is an initial study towards the analysis of fire and smoke propagation in underground green corridors.

The use of a passive dissipation system on a building reduces energy consumption and improves energy efficiency. This technology is important considering that in the EU more than 40% of primary energy consumption for heating and cooling derive by the construction sector. This article reports the effects of a green wall, spaced 60 cm from the building wall, placed on a demonstration building at the ENEA Casaccia Research Center. The values of global solar radiation parameters, wall surface temperature, relative humidity inside and outside the interspace between the green wall and the building were detected. The results show that plant greening on the building reduces heat flux into the building, by reducing air temperature of building wall, especially in summer.

Existing studies emphasizing the magnitude of green-wall thermal benefits paid little attention to temporal microclimatic behavior. To bridge the knowledge gap, we employed high-precision sensors to monitor the microclimate of two wirerope-type climber green walls and adjacent control bare walls in humid-subtropical Hong Kong. Sample days were systematically selected to represent the results on sunny, cloudy and rainy weather in summer. This study aimed at: (1) evaluating the magnitude and daily temporal occurrence of maximum temperature, cooling and insolation at different positions of the layered green walls, and (2) analyzing temporal occurrence patterns of maximum values of microclimatic variables. The results demonstrated the paramount importance of insolation on green-wall microclimate. Varied solar inputs under different weather brought a sequence in maximum insolation, temperature and cooling: sunny > cloudy > rainy. Achieving an average cooling of 8.5 °C against bare wall surface exterior on sunny days, climber foliage acted as a heat sink for the street canyon and the building shell. The posterior air gap (PAG) generated an effective insulation layer with average cooling of 2.5 °C against ambient air in sunny conditions. However, ambient air anterior to the green wall experienced minor warming up to 0.05 °C. Cooling was stronger on more solar-exposed aspect and under stronger insolation. Green walls steered humidification effect by 0.17 kPa on average on sunny days. Daily temperature oscillation was moderated most obviously at the building exterior with average 4.3 °C reduction in sunny conditions. Implications were drawn on climber-species selection and PAG provision to enhance the multi-dimensional thermal benefits of climber green wall.

Purpose Vertical gardens offer multiple benefits in urban environments, including passive cooling services. Previous research explored the use of “active vertical gardens” as potential evaporative air-cooling units by developing a mathematical model based on the FAO-56 Penman Monteith equation. Further research showed that active vertical gardens function best by creating an airflow in the cavity behind the garden such that air is cooled by flowing over the water-saturated garden substrate. The purpose of this paper is to improve the quantification of active vertical garden performance. Design/methodology/approach A building-incorporated vertical garden was built in Quito, Ecuador, with an air inlet at the top of the garden, an air cavity behind the garden and where air was expelled from the base. Measurements were made of air temperature, humidity and velocity at the air inlet and outlet. Findings The active vertical garden cooled the air by an average of 8.1 °C with an average cooling capacity of 682.8 W. Including the effects of pre-cooling at the garden inlet, the garden cooled the air by an average of 14.3 °C with an average cooling capacity of 1,203.2 W. Originality/value The results are promising and support the potential for active vertical gardens to be incorporated into building services and climate control.

The thermo-regulatory function of building-integrated climber vegetation has been verified. However, there is a need to increase in-situ observation studies on green walls installed on windowed building envelopes. This study presents results of instrumental monitoring of the thermal and radiative environment of a climber-green wall with windows to inspire a more energy-efficient green wall system design. This research is based in humid-subtropical Hong Kong, with reference to experimental controls (without vegetation cover) of a bare wall and a bare roof in sunny, cloudy and rainy weather in summer. The experimental results demonstrated lower short-wave reflectivity on green wall (0.13) than on control bare wall (0.30). Green wall received the thermal influence of long-wave terrestrial radiation as well as sky radiation. On sunny, cloudy and rainy days, the exterior concrete wall surface behind climber vegetation was cooler than control bare wall up to 6.6, 2.3 and 1.2 K respectively, and the posterior air gap shielded by the climbers was cooler than ambient air up to 2.2, 0.8 and 0.4 K. On sunny day, indoor wall surface and air of the green wall envelope were warmer at maximum by 1.4 and 1.3 K respectively, possibly contributed by the thermal bridge effect of the windows. On cloudy and rainy days, however, indoor surface and air experienced cooling by

Green walls, installed on the side of the buildings, mainly for their aesthetics and micro climate benefits, could become effective on-site greywater treatment solutions. However, far more research is needed to convert these nature-based systems into low-cost water purification technologies. This process study presents the first step in development of greywater-treating green walls by examining how variation in plant spaces and operational conditions (hydraulic loading rate, inflow concentrations and intermittent drying) influence nutrient removal from light greywater. The experiment was conducted over 12 months on a large-scale pilot green wall located in a laboratory in Melbourne, Australia. The results showed that ornamental plant species can successfully adapt to greywater only irrigation regime and play an important role in nitrogen and phosphorus uptake from greywater. Higher performing plants, C. appressa, N. obliterate, M. parvifolium and L. muscari, had on average 7–10% higher TN removal than unvegetated configuration (over 88% removal overall), which is attributed to consistently high NOx uptake. On the other hand, poorer performing plants O. japonicus, P. occidentalis and N. officinale tended to leach NOx, likely due to their shallow or slow developing root systems. While low retention times hindered high TP removal from all tested configurations, high dependency on plant species and operational conditions was still observed, with C. appressa and N. obliterata being the two highest performing plants (34–53% removal during standard operation). The overall phosphorus uptake was found to improve over time, suggesting that plant growth is a significant TP removal mechanism in green walls. While drying caused a performance drop for all designs, higher performing plant species were less affected by changes in operational conditions. The tested configurations showed good resilience to sudden inflow concentration increases, suggesting green walls could be used as a robust and aesthetically attractive on-site greywater treatment system.

Climber green wall can alleviate urban heat island and conserve energy, mainly attributed to shading of solar irradiance by vegetation, yet the mechanism has remained poorly understood. The radiation properties of transmissivity, reflectivity and absorptivity, and thermal properties of the building envelope equipped with green wall, jointly govern radiation transfer processes. This field-experimental study monitored in-situ the radiation regime of a climber green wall on a windowed building envelope using high-precision radiometers. The northeast-oriented green wall in humid-subtropical Hong Kong has Lonicera japonica climbers, with 0.24 leaf area index. Radiation properties and shading-induced energy savings were determined in summer and validated. An innovative radiation apportionment model (RAM) was developed to determine the short-wave transmissivity, reflectivity and absorptivity of the climber canopy which were respectively 0.382, 0.074 and 0.543 in sunny weather and 0.449, 0.098 and 0.454 in cloudy weather. For further model development, the extinction coefficient (κ) obtained from Beer’s Law was estimated at 4.00 and 3.34 in respective weather conditions. According to RAM outputs, shading alone could shield against insolation up to 497 W/m2 behind the canopy and 356 W/m2 in the indoor space. Taking the electricity tariff and the carbon intensity of electricity generation of a local power company, the average daily energy savings at 0.226 kWh/m2 were translated into monetary and carbon units, registering approximately USD0.03 and 0.062 kg CO2 respectively. The extrapolated seasonal savings from a total of six green walls installed at the experimental site could reach USD75.8 and 157.9 kg CO2.

The installation of urban green infrastructure, particularly green walls, has proven to be an effective strategy for the mitigation of particulate matter (PM) pollution and the urban heat island effect. For the interaction between vegetation, PM and the local microclimate, wind flow is the main driving force. In order to investigate these interactions in detail, it is important to know how air flows through vegetation. This study proposes a method based on the DarcyForchheimer equation, where vegetation is considered as a porous medium and several plant species and the effects of plant morphological characteristics are examined both experimentally and using computer simulations. Results showed that the DarcyForchheimer model is a simple and robust way to describe air flow through vegetation regardless of its morphology. This research provides a new vision on studying aerodynamic properties of vegetation in relation to their morphology and provides opportunities for model the interaction between vegetation and its environment.

A mathematical model that governs unsteady coupled moisture and heat energy transport through an exterior wall covered with vegetation is described. The unknown temperature and moisture content of the plants and canopy air are represented by a system of nonlinear ordinary differential equations (ODEs). The transport of moisture and heat through the support structure, which includes insulation and soil layers, is defined in a series of nonlinear partial differential equations (PDEs). After setting out the model, this article presents and discusses a set of numerical applications. First, a simplified system consisting of a brick wall covered with climbing vegetation is used to study the role of individual variables (e.g., wind speed, minimum stomatal internal leaf resistance, leaf area index, and short-wave extinction coefficient) on the hygrothermal behaviour of the green wall. Thereafter, more complex green wall systems comprising a bare concrete wall, mortar, cork-based insulation (ICB), soil and vegetation are used to evaluate the influence of the thermal insulation and substrate layers on the heat flux distribution over time at the interior surface of the wall, and on the evolution of the relative humidity, water content, and temperature throughout the cross section of the green wall. The numerical experiments proved that vegetation can effectively reduce exterior facade surface temperatures, heat flux through the building envelope and daily temperature fluctuations.

The green wall concept has been introduced as one of the solutions to reduce energy demand for ventilation requirements while improving the natural vegetation in dense urban areas. Past studies revealed that the energy-saving of green walls can vary substantially, from 35% to 90% across countries such as United Kingdom (UK), Canada, Russia, Greece, China, Saudi Arabia, India, and Brazil. Given these differences in energy saving of green walls due to climatic conditions and other reasons, direct application of such findings to the Sri Lankan context is questionable. Therefore, this study aimed to assess the thermal performance of green wall applications in Sri Lanka through a case study analysis of an indirect green façade with a comparative conventional wall. The required data were extracted through on-site temperature measurements from different points of both the exterior and interior wall surfaces of each building in different time intervals per day for a period of fourteen days spanning from October to November. The analysis shows that the green walls contribute to 21% - 36% of temperature difference compared to the conventional wall. Eventually, this results in 0.06 kWh of energy-saving per m2 of wall area, and thereby green walls contribute to the 80% energy saving for ventilation requirements. Hence, the study recommends that the use of green walls can be considered as one of the energy efficiency solutions while improving natural vegetation in tropical climatic cities and absorbing other benefits of green walls.

In this study, it is aimed to determine the results of the usage of vertical green façade and green roof systems which are increasing in use today, in four different climatic zones of our country, considering the annual heating, cooling and total energy consumption. Based on a building model in the study, the effect of the green facade and green roof applications on the buildings' annual heating and cooling loads was tried to be determined for four cities of our country with four different climatic characteristics. In selected cities in these climate regions, a traditional building and buildings with vertical green facades and green roof applications were compared. Situated in Turkey's four different climatic zones with the results achieved in this study was found to be differences in four different city's annual energy consumption. In the annual total energy consumption; Antalya city with 2.68% as a result of application of only planted roof systems, Konya city with 11.64% as the result of application of only vertical green façade systems, and highest benefit rates in Erzurum city with application of both systems and 14.38% at the end. As a result of this, considering the annual total energy consumption, green facades and green roof applications in buildings are found to have a positive effect on the energy performance of the building, even though it does not vary from region to region., Bu çalışmada, günümüzde kullanımı artan düşey yeşil cephe ve yeşil çatı sistemlerinin ülkemiz sınırlarında dört farklı iklim bölgesindeki kullanımının yıllık ısıtma, soğutma ve toplam enerji tüketimleri dikkate alındığında ne gibi sonuçlar vereceğinin tespit edilmesi amaçlanmıştır. Çalışmada, bir bina modeli esas alınarak düşey yeşil cephe ve yeşil çatı uygulamalarının, binaların yıllık ısıtma ve soğutma yüklerine etkisi, ülkemizin dört farklı iklim özelliğine sahip dört kenti için belirlenmeye çalışılmıştır. Bu iklim bölgelerinde seçilen kentlerde, geleneksel bir bina ile düşey yeşil cephe ve yeşil çatı uygulamalarının kullanıldığı binalar karşılaştırılmıştır. Ulaşılan sonuçlar ile Türkiye’nin dört farklı iklim bölgesinde yer alan dört farklı kentin yıllık tüketim enerjilerinde farklılıklar olduğu saptanmıştır. Yıllık toplam enerji tüketiminde; sadece bitkilendirilmiş çatı sistemlerinin uygulanması sonucunda %2.68 ile Antalya kenti, sadece düşey yeşil cephe sistemlerinin uygulanması sonucunda %11.64 ile Konya kenti, her iki sistemin uygulanması soncunda ise %14.38 ile Erzurum kentinde en yüksek fayda oranları sağlanmıştır. Bunun sonucunda, yıllık toplam enerji tüketimleri dikkate alındığında, binalarda yeşil cephe ve yeşil çatı uygulamalarının, bölgeden bölgeye farklılık göstermesine rağmen binanın enerji performansını olumlu yönde etkilediği saptanmıştır.

Poor indoor quality affects people’s health and well-being. Phytoremediation is one way in which this problem can be tackled, with living walls being a viable option for places with limited space. The aim of this study was to evaluate the efficiency of five plant species in a living wall to remove Volatile Organic Compounds (VOCs) and to identify whether the type of pollutant has any influence. An enclosed chamber was used to add the contaminants n-hexane and formaldehyde independently. Total VOCs were measured for three days in two scenarios: (1) empty chamber, and (2) chamber with living wall. Five living walls were prepared, each with three plants of the same species: Spathiphyllum wallisii, Philodendron hederaceum, Ficus pumila, Tradescantia pallida, and Chlorophytum comosum. There was no correlation between leaf area/fresh weight/dry weight and the contaminant reduction. In general, all five species were more efficient in reducing TVOCs when exposed to formaldehyde than to n-hexane. Chlorophytum comosum was the most efficient species in reducing the concentration of TVOCs for both contaminants, Spathiphyllum wallisii being the least efficient by far.

Green walls are vertical greening structures where varied plant species grow. They are conceived as a form of urban landscape and have numerous environmental, social and economic benefits. In fact, these structures have positive effects on air quality, thermal and acoustic insulation, microclimate, psychophysical well-being and urban design. In the framework of thermal comfort, several studies demonstrated the potential of green walls to improve indoor thermal comfort and reduce heat flows through the wall of buildings. This research evaluates the thermal efficiency of two modular green walls that present an alternative substrate as growing medium. This substrate is composed of loam soil and rice husk, an agricultural organic waste derived from the rice milling process. The choice of rice husk is inspired by principles of circular economy in order to reduce the environmental impact and costs of the substrate used in greening applications. The alternative substrate was compared with expanded clay aggregate, used for plant cultivation in living walls, and the analysis was divided into two phases. Firstly, field experiments were carried out on three plant species (Chlorophytum, Dieffenbachia and Spathiphyllum) to evaluate the efficacy of these substrates to grow plants. The efficacy of the substrate was evaluated through the measurement of the concentration of chlorophyll, the determination of the growth index of plants and a qualitative observation of the root development. Secondly, two modular green walls with varied substrates and plants were designed and tested from the point of view of the thermal comfort, using the open source software TerMus-G. After the transmittance value was obtained as output for each green wall module, the heat flow and the relative variation were calculated and compared to the indoor supporting walls. This article presents a valid methodology approach to evaluate the efficiency of green walls substrate and its thermal performance. This methodology differs from those found in scientific literature and represents a valid alternative. The present research demonstrates the ability of designed modules and, more generally, of indoor green walls to increase thermal insulation without causing condensation. Furthermore, the investigation shows a positive contribution both in winter and in summer. Finally, the use of this undervalue by-product rice husk mixed with loam soil shows to be appropriate for green wall application, providing better performance than the expanded clay in terms of thermal comfort and plant growth rate. Moreover, its use as substrates should further improve the ecological footprint of green vertical structures and reduce costs.

Urban densification continues to present a unique set of economic and environmental challenges. A growing shortage of green space and infrastructure is intrinsically linked with urban growth and development. With this comes the loss of ecosystem services such as urban heat island effects, reduction of air quality and biodiversity loss. Vertical greenery systems (VGS) offer an adaptive solution to space-constrained areas that are characteristic of dense urban areas, and can potentially improve the sustainability of cities. However, in order to promote VGS uptake, methods are required to enable systematic appraisal of whether existing walls can be retrofitted with VGS. Further, feasibility studies that quantify the potential for retrofit suitability of VGS across entire urban areas are lacking. This study established an evaluation tool for green wall constructability in urban areas and validated the assessment tool by determining the quantity of walls in five major Australian cities that could potentially have VGS incorporated into the existing infrastructure. Each wall was analysed using an exclusionary set of criteria that evaluated and ranked a wall based on its suitability to VGS implementation. Sydney and Brisbane recorded the greatest proportional length of walls suitable for VGS, with 33.74% and 34.12% respectively. Conversely, Perth's urban centre was the least feasible site in which to incorporate VGS, with over 97% of surveyed walls excluded, mainly due to the prevalence of

Currently no sustainable, economical and scalable systems have been developed for the direct removal of roadside air pollutants at their source. Here we present a simple and effective air filtering technology: botanical biofiltration, and the first field assessment of three different botanical biofilter designs for the filtration of traffic associated air pollutants – NO2, O3 and PM2.5 – from roadside ambient air in Sydney, Australia. Over two six month research campaigns, we show that all of the tested systems filtered NO2, O3 and PM2.5 with average single pass removal efficiencies of up to 71.5%, 28.1% and 22.1% respectively. Clean air delivery rates of up to 121 m3/h, 50 m3/h and 40 m3/h per m2 of active green wall biofilter were achieved for the three pollutants respectively, with pollutant removal efficiency positively correlated with their ambient concentrations. We propose that large scale field trials of this technology are warranted to promote sustainable urban development and improved public health outcomes.

The use of vertical greenery systems in buildings is becoming more and more common as they provide several benefits, particularly in improving indoor thermal comfort. This paper studies the influence of an indoor living wall on the air temperature and humidity in the test house in Ho Chi Minh City. Effects of the plants, irrigation and ventilation were examined. The temperature and humidity were monitored and analyzed during a 2–month period. The cooling effect of the living wall was proven, with an average reduction of 1°C of the room temperature. Higher air humidity levels were experienced near the green wall, increasing the overall humidity in the room. Irrigation for the plants also helped reduce the room temperature compared to that without irrigation. Therefore, these systems have been proven to be very useful and interesting for warm indoor environments due to the cooling effect.

In hot, humid, subtropical climates, strong solar radiation imposes heat stress upon building users, who often resort to air conditioning in a bid to improve indoor thermal comfort. Green walls are a nature-based solution to this enormous cooling need. The foliage of climber vegetation can reduce the shortwave radiative penetration into the indoor space of windowed building envelopes. This chapter presents a revised radiation apportionment model (RAM*) for estimating the benefits of shading against shortwave radiation as a cooling-load reduction. Adhering to the principles of an improved radiative transfer model, field data harvested from net radiometers were input into a Microsoft Excel spreadsheet. The Solver function determined the radiative properties of various layers of windowed building envelopes featuring a climber green wall. The radiative transmissivity (τ), reflectivity (ρ), and absorptivity (α) were 0.366, 0.079, and 0.555, respectively. Using objectively selected sunny days, daily reductions in electricity use, electricity tariff, and carbon dioxide emissions were 0.44 kWh, 0.07 USD, and 0.29 kg, respectively, for a square meter basis of the climber green wall featured in this study. Corresponding savings in a cloudy scenario were reduced to 0.25 kWh, 0.04 USD, and 0.16 kg. The RAM* features two major improvements, namely the reduction of bias due to manually input radiative properties of artificial building materials and the addition of iterative radiative transfer pathways. By approximating the potential shading-induced cooling, the RAM* fosters an evidence-based approach for practitioners in green building designs.

According to the European Research and Innovation Policy Agenda, nature-based solutions (NBSs) are key technologies to improve the sustainability of urban areas. Among NBSs, green walls have been recently studied for several applications, among the others the treatment of lowly polluted wastewater flows as greywater (GW, e.g. domestic wastewater excluding toilet flushes). This work is aimed at the evaluation of the influence of four additives (compost, biochar, granular activated carbon, polyacrylate) mixed with a base filter medium made of coconut fibre and perlite, on the performances of a green wall fed in batch mode with synthetic GW. The green wall was operated with a high hydraulic loading rate of GW (740.8 L/m2/day) in open-air winter conditions (3.5–15 °C measured for GW) between January and April. The performances of the green wall have been assessed though the monitoring every 1–2 weeks of physicochemical and biological parameters (pH, electric conductivity, total suspended solids, dissolved oxygen, BOD5 and COD, nitrogen and phosporus compounds, chlorides and sulphates, anionic surfactants and E. coli). Removal performances were excellent for BOD5 (>95%) and E.coli (>98%) for all additives; compared to the base medium, biochar was the best performing additive over the highest number of parameters, achieving removals equal to 51% for COD, 47% for TKN and nitric nitrogen and 71% for anionic surfactants. Compost also achieved high removal performances, but the frequent clogging events occurred during the monitoring period do not make its use recommendable. Granular activated carbon and the combination of biochar and polyacrylate performed better than the base medium, but only about the removal of nitric nitrogen. These results demonstrated that, in the considered experimental boundaries, biochar could improve the overall treatment performances of a green wall fed by GW and operated in challenging conditions.

The building and construction sector is a large contributor to anthropogenic greenhouse gas emissions and consumes vast natural resources. Improvements in this sector are of fundamental importance for national and global targets to combat climate change. In this context, vertical greenery systems (VGS) in buildings have become popular in urban areas to restore green space in cities and be an adaptation strategy for challenges such as climate change. However, only a small amount of knowledge is available on the different VGS environmental impacts. This paper discusses a comparative life cycle assessment (LCA) between a building with green walls, a building with green facades and a reference building without any greenery system in the continental Mediterranean climate. This life cycle assessment is carried according to ISO 14040/44 using ReCiPe and GWP indicators. Moreover, this study fills this gap by thoroughly tracking and quantifying all impacts in all phases of the building life cycle related to the manufacturing and construction stage, maintenance, use stage (operational energy use experimentally tested), and final disposal. The adopted functional unit is the square meter of the facade. Results showed that the operational stage had the highest impact contributing by up to 90% of the total environmental impacts during its 50 years life cycle. Moreover, when considering VGS, there is an annual reduction of about 1% in the environmental burdens. However, in summer, the reduction is almost 50%. Finally, if the use stage is excluded, the manufacturing and the maintenance stage are the most significant contributors, especially in the green wall system. This work was partially funded by the Ministerio de Ciencia,Innovación y Universidades de España (No. RTI2018-093849-B-C31 – MCIU/AEI/FEDER, UE) and by the Ministerio de Ciencia, Inno-vación y Universidades – Agencia Estatal de Investigación (AEI)(No. RED2018-102431-T). The authors at GREiA would like tothank the Catalan Government for the quality accreditation givento their research group (2017 SGR 1537). GREiA is a certified agentTECNIO in the category of technology developers from the Govern-ment of Catalonia. This work is partially supported by ICREA underthe ICREA Academia programme.

Vertical greenery systems (VGS) has gained its popularity in the modern cities as it is proven to have various benefits, among which thermal benefits to achieve energy saving on buildings are significant. Current studies have been primarily focused on evaluating the impact of VGS on building energy use through reducing conduction heat gain, however, the energy consumed in producing, transporting, installing and maintaining the VGS has not been fully investigated. As most VGS supporting components are made of energy intensive materials, such as steel pipe and frame, it is essential to quantify the total energy consumed by VGS during its entire life-cycle stage for a better evaluation and propagation of VGS. The aim of this study is to explore the environmental impacts and the sustainability of VGS from the lifecycle energy (LCE) perspective. Specifically, the objectives are as follows: first to determine the overall LCE of three types of systems; and to identify the components with the highest impacts on LCE; finally, to recommend strategies to help the industry better manage the LCE of VGS. In this study, the life cycle energy analysis (LCEA) has been used to effectively capture the LCE generated from initialization, installation, maintenance, demolition of VGS. The energy data in each stage were collected from three types of VGS projects in Singapore that include carrier, planter and support system. From the results, carrier system is found to consume the highest LCE, followed by planter system and support system. When comparing the LCE with the energy that saved from lower building cooling load, it requires roughly 6.5–11.8 years to reach a balance of zero energy for different systems. The study is the first to present LCE of VGS in tropical climate and the results can be used as a reference for the future selection of VGS as well.

Graywater (GW), i.e., the portion of household wastewater that excludes toilet flushes, is an interesting wastewater type because it requires only mild treatment. Green walls have been proposed as ...

The advantages of low-impact development approaches, such as green walls in an urban environment, are numerous. These systems can be applied for managing stormwater, saving energy consumption, decreasing noise pollution, improving runoff quality, improving life quality, and so forth. Besides, atmospheric water harvesting methods are considered a nonconventional water source. There are many studies about the analysis and advantages of green walls and atmospheric water harvesting conducted separately. However, the use of a combined system that uses fog harvesting in the irrigation of green walls has received less attention in previous studies, and therefore in this research, the feasibility of a novel green wall platform was investigated. At first, the potential of using green walls and atmospheric water harvesting in different climates was analyzed. Then a new combined system was proposed and explained. The study results determined that atmospheric water harvesting can be applied as a source of irrigation for green facilities, particularly in the dry season and in periods with lower precipitation. In the Mediterranean climate, summer fog harvesting yields 1.4&ndash, 4.6 L/m2/day, and the water consumption of green walls is about 4&ndash, 8 L/day/m2. This can improve one issue of green walls in an urban environment, which is irrigation in summer. Furthermore, the novel system would protect plants from severe conditions, improve buildings&rsquo, thermal behavior by decreasing direct sunlight, and increase conventional green walls&rsquo, efficiency and advantages.

Although the benefits of vegetation are widely known, its use as a facade element remains a very incipient practice. This strategy has become popular due to the promise of improvement on the thermal performance of buildings, in addition to representing an alternative for expanding biodiversity in the urban environment. This paper investigates the influence of green walls, within the Brazilian climate context, on the thermal performance of social housing buildings. The methodology consists of the simulation of the thermal and energy behavior of a multifamily housing building. The simulation is performed with the EnergyPlus® program, including the HAMT model, that takes into account the moisture transfer process through the envelope for three bioclimatic zones provided by the Brazilian standard NBR 15520-2005: extreme winter climate (ZB1), extreme summer climate (ZB8), and a climate considered as the intermediary (ZB3). The results obtained demonstrate a difference in the environments' indoor temperature caused by the two facade arrangements: with and without vegetation. The green wall's use provided a reduction in the indoor temperature of up to 2.8 °C in summer and an increase of up to 1.4 °C in winter. The facade's vegetation worked as a layer of thermal insulation, helping to keep the indoor temperature lower during the day and mild during the night. Therefore, green walls can represent a sustainable and low-cost solution to be implemented in buildings, aiming to improve their thermal performance.

The ‘Black Summer’ wildfires that affected Australia over the 2019–2020 summer have led to concern over the health effects of exposure to wildfire emissions, and generated a need for means to reduce exposure. Recently, active green infrastructure has been implemented in cities to assist in the removal of urban air pollution, however the filtration of wildfire emissions has not been previously tested. Here, we field trial botanical biofiltration for the reduction of elevated air pollutant concentrations associated with Black Summer. Two active green walls were installed in outdoor environments in Sydney over Black Summer, with the concentrations of NO2, O3 and PM2.5 in ambient and filtered air streams monitored over 14 days with elevated air pollution concentrations due to wildfire emissions. Average pollutant single pass removal efficiencies of 63.17%, 38.79% and 24.84% for NO2, O3 and PM2.5 respectively were recorded, with clean air delivery rates of 558.90 m3/h, 343.19 m3/h and 219.77 m3/h for NO2, O3 and PM2.5 respectively for each 5 m2 biofilter wall. Weak negative associations were observed between the removal efficiency of NO2 and PM2.5 and their corresponding ambient concentrations. Strategic employment of botanical biofiltration may thus be of value in reducing wildfire emissions in sensitive populations.

The experimental study of vegetated walls and their effects on humidity, air temperature and CO2is essential. This paper presents an experiment on a green wall to apprehend its thermal and hydrological behavior and its impact inside the building. The experiment is based on a living wall set up in a classroom. Monitoring of temperature, humidity and CO2 variations within the living wall and a reference case enabled us to analyze the effects of green walls. Measurements were performed in Kosice, a city in Slovakia. During the measurements, a set of questions were answered. The data from the respondents were used to achievethe goal of this interdisciplinary research, which was to identify the effect of green walls on the well-being of people. It can be stated that women are more sensitive to changes than men. Following the measurements, it can be stated that the green wall is very favorable for indoor environments. The optimum relative air humidity in rooms such as classrooms, hotels and theaters is from 30% to 70%. From a relative humidity perspective, green walls appear to be beneficial for indoor buildings.

The paper presents an experiment on green wall performed to apprehend its thermal and hydrological behavior and its impact inside building. The experiment is based on a living wall set up in a classroom of the faculty in TUKE campus in Kosice where the interior green wall is situated. Monitoring of temperature, humidity and CO2 variations within the living wall and a reference case enable us to analyze effects of green walls. During the measurements, set of questions were answered. The data of respondents are used for gaining the goal of this interdisciplinary research, the effect of green wall on the well-being of people. The measurements were carried out in the classroom between January 04, 2018 and February 08, 2018. It can be stated that women are more sensitive to changes than men. Following the measurements, the green wall is very favorable for the indoor environment.

© 2020 Elsevier Ltd Indoor air quality (IAQ) is of growing public health concern which has prompted the use of plants to phytoremediate air pollution in interior spaces. Active green walls are emerging as a means of reducing indoor contaminants and have demonstrated efficacy comparable to conventional air filtering technologies. However, the use of active airflow through organic substrates has the potential to emit bioaerosols into the surrounding environment, where the potential risk to human health is largely unknown. In this study, we demonstrate that two indoor green walls (with and without active airflow) contribute significantly to the ambient fungal load, however concentrations remained well below WHO safety guidelines. Bacterial dynamics within the rhizosphere/substrate of the operational botanical biofilters displayed variability across plant species. Phyla-wide distribution generally aligned with previous literature; however, differences from those previously reported were observed at the genus level, possibly due to geographic location, substrate composition, or plant species selection. Targeted assessment of Legionella aerosol contamination, an under-addressed potential pathogen for these active systems, yielded no positive identification during the sampling period. We conclude that active green walls host a unique bacterial profile and do not emit harmful levels of fungal propagules or pose significant risk of aerosolised Legionella species, provided systems are well monitored and maintained.

Green walls have previously demonstrated the capacity to reduce particulate matter (PM), noise pollution, and temperature conditions in manipulative experiments and computational models. There is, however, minimal evidence that green walls can influence ambient environmental conditions, especially taking into account the variable environmental conditions encountered in situ. The aim of this paper was to determine if green walls have a quantitative effect on ambient air quality in an urban environment. Ambient PM, noise, and temperature were recorded at 12 green wall and adjacent reference wall locations across a dense urban centre, over a 6-month period. The results indicated that PM levels and temperature did not significantly differ between the green wall and reference wall sites. Ambient noise at the green wall sites, however, was significantly lower than at the reference wall locations. It is suggested that mechanically assisted, or &lsquo, active&rsquo, green wall systems may have a higher PM and temperature reduction capacity, and if so, they will be more valuable for installation in situ compared to standard passive systems, although this will require further research.

Hot and dry climate and air pollution is a growing problem in urban areas, and this can have an adverse impact on life and health of urban residents. One of the ways to protect people from this hazard is the use of urban green or street greenery. However, its implementation can be problematic in highly urbanized areas. This paper presents a concept of the green structure (GS), designed, and is still being developed, by Adam Kalinowski where cooling efficiency is based on the synergy of shade and evapotranspiration. The GS that could be used as street furniture, small architecture form or a public utility structure intended to protect people and objects from an adverse urban environment, at the same time providing pleasant and healthy microclimate inside. The pilot project-the first application of the GS in the urban environment-is presented and the results of short-term measurements of temperature and humidity are provided and analyzed. Moreover, a simple dynamic simulation of the GS performance in courtyards has been conducted. The obtained results show the decrease of the perceived temperature within this structure. Depending on climate type, an average potential reduction of Universal Thermal Comfort Index (UTCI) and mean radiant temperature (Tmrt), caused by the GS in a courtyard case study, is 5–8 °C and 17–29 °C, respectively. Performed simulation also confirms that TRNSYS software is an appropriate tool for simple outdoor microclimate analysis. Further research to develop this concept, increase its performance and customize it for different applications are proposed.

In cities with dry arid climate, air conditioning (AC) equipment is necessary for thermal comfort in indoor spaces. The use of this equipment generates an increase in electricity consumption and an increment in CO₂ emissions to the environment, thus, one way to mitigate these negative effects is the Living Green Wall (LGW). The objective of this research is to assess the decrease in thermal gain, energy benefits, and estimate the greenhouse gas (GHG) emissions that are not emitted by the use of the LGW. Measurements of heat flux, solar radiation, and temperatures were made on a concrete wall and another with an LGW in a west-facing building in the city of Mexicali, Mexico. The results indicate that it is possible to reduce 49% of the heat flow through the wall, which reduces the thermal load 102,212 Btu/h to the indoor space, implying the additional work of 8.53 tons of AC. This excess equals 985.6 kWh of electrical energy and generates a total of 697 kg of CO₂ emissions during the warm season. It is concluded that shading with an LWG becomes a very influential element to mitigate the heat fluxes towards the indoor spaces.

With the increasing number of migrants and refugees, there is a need for energy-efficient and low impact temporary housing that can accommodate millions of displaced peoples worldwide. This study describes a design proposal for a premium passive refugee house that uses three main passive heating and cooling solutions (Earth Air Heat Exchanger, Trombe wall, and green wall) and is suited to the Swedish climate. The purpose of the combination of the three passive systems is to reduce cooling and heating loads to conserve a significant amount of primary energy and thus mitigate the impact of the house's energy use on the environment through a reduction in emissions. The house is designed to fulfill its energy needs from renewable sources and produce an annual surplus of 180 kWh/m 2/annum. The methodology applied is a dynamic system modeling and simulation approach using TRNSYS and ANSYS software. The simulation results showed a heating load of 7.9 kWh/m 2/annum and a cooling load of 2.8 kWh/m 2/annum, with total energy consumption reaching 18.4 kWh/m 2/annum. Preliminary feasibility costing showed a payback time of 7.4 years out of the 25-years suggested lifetime of building using the three passive solutions. The amount of CO 2 emissions is 231.1 kg CO 2e/annum with a primary energy demand of 0.032 GJ/m 2/annum. As a follow-up to the initial study, a proof of concept has been implemented in Lund, Sweden, in an urban living lab to verify the simulation results through a 12-month post-occupancy monitoring and evaluation study.

A sustainable technology for improving the energy efficiency of buildings is the use of urban greening in order to reduce the energy consumption for air conditioning in summer and to increase the thermal insulation in winter. A worldwide growing interest in urban green is encouraging the application of the greening technology for more sustainable buildings. Building indoor air temperature depends on several different parameters related to the climate of the region, the building itself and its use. The main parameters influencing the microclimate are: external air temperature and relative humidity, incident solar radiation, long wave radiation exchange between the building surfaces and its surroundings, wind velocity and direction, air exchanges, physical and thermal properties of the building's envelope materials, design variables such as building dimensions and orientation, presence of artificial light, electrical equipment. Green façades can allow the physical shading of the building and promote evapotranspiration in summer and increase the thermal insulation in winter. External wall surface temperature is a parameter useful to assess the effectiveness of green façades. An experimental test was carried out at the University of Bari (Italy) for three years. Three vertical walls, made with perforated bricks, were tested: two were covered with evergreen plants (Pandorea jasminoides variegated and Rhyncospermum jasminoides) while the third wall was kept uncovered and used as control. Several climatic parameters concerning the walls and the ambient conditions were collected during the experimental test. The experimental data were used for developing a multiple regression equation regarding the dependence of the difference of external surface temperature between the green façades and the control wall and the weather conditions. The model shows a good predicting ability.

© 2018, Springer Nature B.V. Atmospheric pollutant phytoremediation technologies, such as potted plants and green walls, have been thoroughly tested in lab-scale experiments for their potential to remove air pollutants. The functional value of these technologies, however, is yet to be adequately assessed in situ, in ‘high value’ environments, where pollutant removal will provide the greatest occupant health benefits. Air pollution in countries such as China is a significant public health issue, and efficient air pollution control technologies are needed. This work used pilot-scale trials to test the capacity of potted plants, a passive green wall and an active green wall (AGW) to remove particulate matter (PM) and total volatile organic compounds (TVOCs) from a room in a suburban residential house in Sydney, Australia, followed by an assessment of the AGW’s potential to remove these pollutants from a classroom in Beijing. In the residential room, compared to potted plants and the passive green wall, the AGW maintained TVOCs at significantly lower concentrations throughout the experimental period (average TVOC concentration 72.5% lower than the control), with a similar trend observed for PM. In the classroom, the AGW reduced the average TVOC concentration by ~ 28% over a 20-min testing period compared to levels with no green wall and a filtered HVAC system in operation. The average ambient PM concentration in the classroom with the HVAC system operating was 101.18 μg/m 3 , which was reduced by 42.6% by the AGW. With further empirical validation, AGWs may be implemented to efficiently clean indoor air through functional reductions in PM and TVOC concentrations.

© 2018 Elsevier Ltd Poor air quality is an emerging world-wide problem, with most urban air pollutants arising from vehicular emissions. As such, localized high pollution environments, such as traffic tunnels pose a significant health risk. Phytoremediation, including the use of active (ventilated) green walls or botanical biofilters, is gaining recognition as a potentially effective method for air pollution control. Research to date has tested the capacity of these systems to remove low levels of pollutants from indoor environments. If botanical biofilters are to be used in highly polluted environments, the plants used in these systems must be resilient, however, this idea has received minimal research. Thus, testing was conducted to assess the hardiness of the vegetated component of a botanical biofilter to simulated street level air pollutant exposure. A range of morphological, physiological, and biochemical tests were conducted on 8 common green wall plant species prior to and post 5-week exposure to highly concentrated diesel fuel combustion effluent; as a pilot study to investigate viability in in situ conditions. The results indicated that species within the fig family were the most tolerant species of those assessed. It is likely that species within the fig family can withstand enhanced air pollutant conditions, potentially a result of its leaf morphology and physiology. Other species tested were all moderately tolerant to the pollution treatment. We conclude that most common green wall plant species have the capacity to withstand high pollutant environments, however, extended experimentation is needed to rule out potential long term effects along with potential decreases in filter efficiency from accumulative effects on the substrate. MS capsule summary: The results obtained from the multi-trait plant health assessment provide proof-of-concept that active botanical biozfilters are able to withstand short term, high level pollutant exposure.

The process of rapid urbanisation is becoming problematic due to the reduction in, and lack of compensation of, previously vegetated areas. With a combination of green roofs and green walls, adopted on a large scale, it is possible to attenuate the urban heat island effect and internal temperatures in buildings. Tall buildings are becoming a common housing type in many cities, and considering the role of external walls in heat gain, it is expected that the combination of green roofs and green walls have great potential to improve thermal performance. As only 1-2% is added to the total stock of buildings annually, the focus should be on the retrofit of existing buildings to deliver maximum thermal benefits. In the present work lightweight, modular vegetated systems were adopted for roofs and walls. Instead of considering only the temperature influence in heat stress, this research adopted the use of heat index that encompasses the combined effect of temperature and relative humidity. For this purpose, the thermal benefits of green roof and green wall retrofit is evaluated in two small scale experiments, where identical prototypes (vegetated and non-vegetated) are compared using block work and timber framed drywall structures for Rio de Janeiro, Brazil and Sydney, Australia, respectively. The results show a different understanding in heat stress evaluation regarding heat index rather than temperature itself, especially under high levels of relative humidity. This evidence demonstrates green roof and green wall retrofit offer a proven role in heat stress attenuation in residential buildings.

Climate change will lead to increased frequencies of weather extremes in Central Europe, such as severe heat waves and droughts, causing high stress intensities for plants. Drought stress also represents a critical factor on many re-cultivated areas with poor edaphic conditions and small soil depths. This includes living wall systems which are applied to cover shotcrete walls and re-integrate them in landscape surroundings. Due to the vertical arrangement of these systems, which limits absorption of rain water, artificial irrigation was considered mandatory, but experimental evidence is lacking. Therefore, we compared soil and plant water relations of test plots on a ‘Green wall’ system with active and deactivated irrigation. During the vegetation period 2017, soil water potential and plant hydraulic parameters (stomatal conductance, relative water content, midday leaf water potential and osmotic potential) of Phleum pratense, the dominating grass on study plots, were measured. In summer 2017, many weeks with humid weather conditions, but also a pronounced heat period were registered. During this period, considerable physiological responses were observed and respective recovery after subsequent days of heavy precipitation. Phleum pratense showed reductions in stomatal conductance (−148.6 ± 118.8 mmolm−2 s−1), relative water content (−9.3 ± 10.1%) and midday leaf water potential (−0.3 ± 0.5 MPa) on the test plot during heat days. Upon precipitation, differences in water relations between plots ceased within few days. Results indicate that integrated irrigation systems are a necessary component of living wall systems.

Green walls are increasingly being considered as a suitable greywater treatment technology. Nevertheless, until now there have been no clear recommendations for the use of effective lightweight media in greywater treating green walls. Previous studies of potentially suitable growing media have suggested that a combination of perlite and coco coir might be the most effective for these novel systems. However, there is no clear understanding of what proportion of perlite and coir should be used and how different mixes would affect greywater treatment. This work tested the hydraulic and pollutant removal performance of six different perlite and coco coir media mixes in an unvegetated column experiment. The results suggested that there is a point between 2:1 and 3:1 ratios of perlite to coir where the infiltration rate significantly increases, as the result of perlite dominance. As the infiltration rate increases, the mix gets less prone to clogging, but this negatively affects pollutant removal performance, with insufficient time for biological processes. We therefore optimised the mix for effective long-term treatment of total suspended solids, total nitrogen, chemical oxygen demand and Escherichia coli. Unfortunately, total phosphorus removal from greywater was limited for all tested mixes. This study also showed that attention should be given to greywater inflow dynamics and expected daily water treatment capacity; e.g. systems with a lower hydraulic loading were able to use greater proportion of coir in the mix achieving greater water treatment performance, while systems with higher hydraulic loadings require faster flowing mixes with lower coir proportion.